SU1337212A1 - Welding current pulse generator - Google Patents

Abstract

The invention relates to power sources for arc welding and can be used for argon arc welding with non-consumable electrode of aluminum and its alloys. The aim of the invention is to improve the quality of the weld by expanding the range of variation of the parameters of welding current pulses, expanding the functionality of the generator and improving its weight and size parameters. In order to achieve the goal, the power supply is made with the output from the midpoint. In addition, the generator is equipped with additional control keys, one of which is made in the form of a thyristor bridge switch with a capacitor in the diagonal. In a two-section inductive energy storage device, an electric current flows alternately in each of the sections, which allows to receive different-polarity and different-amplitude pulses of the welding current in the arc gap. 3 3.p.f-ly, 7 ill. i (L

Description

The invention relates to power sources for arc welding and can be used for argon arc welding with a non-consumable electrode of aluminum and its alloys, as well as in other fields of technology for powering a load with amplitude pulses of adjustable duration.

The aim of the invention is to noBiii quality of the weld by expanding the range of variation of the parameters of the welding current pulses, expanding the functionality of reHe iaTopa and improving its mass. 15 Different dimensions can be used.

FIG. Figure 1 shows a circuit diagram of a welding current pulse generator in magnetic field, for example, transistors, single-operation and combined-to-off thyristors with artificial switching nodes, locked by thyristor-connected sections of an inductive torus. optoelectronic devices, etc.

energy storage; in fig. 2 - option - Inductive drive is an electromagnetic system consisting of two magnetically coupled

you make a power source; on

FIG. 3 - graph of current through the arc

gap when used in the scheme.

(Fig. l) only the first and second pack-25 on a common ferromagnetic core,

equal keys; in fig. 4 - graph having a non-magnetic gap.

windings arranged as a rule.

and the current through the arc gap when using all controlled keys in the circuit (Fig. 1); in fig. 5 is a basic electrical circuit of a welding current pulse generator when performing an inductive accumulator in the form of two magnetically uncoupled sections; 6, graphs of currents through an arc gap and sections of an inductive energy storage device; in fig. 7 is a diagram of a generator with a controllable key in the form of a thyristor bridge switch with a capacitor in the diagonal.

Welding current pulse generator (fig. O consists of power supply 1, two-part inductive energy storage 2, first 3 and second

ten

In general, the voltage between the third and first terminals can be

the second 4 controllable keys connected to the control unit 5, the first 45 Equal to the voltage between the third and 6 and second 7 output terminals, between the second terminals. For example, in the scheme which includes the arc gap “FIG. 2, b this is achieved with a different 8, with the first pin 9 of the source 1 and the personal number of elements between the power supply through the first controlled key with these pairs of pins, and in the circuit on

3 is connected to the first terminal 10 in- 50 P. A different number of the ductive energy storage device 2, the second turns of the secondary windings by a transformer, the output O of the source 1 of the power supply of the generator. cut the second controlled key 4 connect; with her second; pin 12 inductive FIG. 3 curve 15 is a graph of energy storage 2, the first output 55 through an arc gap 8 at terminal 6 is connected to tap 13 from use — in the circuit (Fig. 1) only the junction of the inductive first and second controlled keys 2. energy storage, source 1 pi - The pulse generator of the welding tube made with the third output 14 ka works as follows.

from the midpoint, which is connected to the second output terminal 7,

The control unit 5 in this case alternately turns on and off the controlled keys 3 and 4 so that the on state of the key 3 always corresponds to the off state of the key 4, and to the switched on state of the key 4 - the off state of the key 3. Duration and the frequency of the on state of the keys is regulated,

As controlled keys to be used various

Roads, for example, transistors, one-operation and -complete-turn off thyristors with artificial switching nodes, lockable thyristor windings, located, as a rule.

Various technical solutions can be used to make the power supply with the third lead from the midpoint. FIG. 2 shows variants of power supply with the third output from the middle point, It can be performed, for example, in the form of a rectifier with a output from the zero point of the secondary winding of the transformer (Fig. 2, a), in the form of a rechargeable battery with the output from a part of the elements (Fig. 2, b), in the form of two series-connected rectifiers (Fig. 2, c) or batteries (Fig 2, d) with the output from the point of their connection, etc.

In general, the voltage between the third and first terminals can be

13

. The arc gap 8 is brought to a conducting state at the moment t (Fig. 3). This can be done with

for example oscillator or by touching

electrode surface of the product. With

supplying a control signal from block 5 to control key 3, it is turned on. In this case, section 10-13 of the inductive energy storage 2 through the on-switch key 3 and the arc gap 8 is charged from the power source 1. The current flows through the circuit of the first output 9 of the power supply source 1 - key 3 - section 10-13 - terminal 6 - arc gap 8 - terminal 7 - the third output 14 of the power supply 1 1. Inductive energy storage 2 is charged by power supply 1. The current through the arc gap 8 increases and flows from terminal 6 to terminal 7, we take this direction as positive. At time t, the control unit 5 switches off the key 3, and the key 4 turns on. Due to the mutual induction between sections 10-13 and 13-12 of inductive storage device 2, the current is intercepted into section 13-12 and flows through the circuit 13-12-41-11-14-7-8-6-13. During the time t - t, the charge of the inductive storage device 2 occurs through section 13-12. The current through the arc gap 8 at the moment t changes its direction in a jump-like manner and through the arc forms a negative current pulse. AT

moment t. the control unit 5 turns on the key 3 again, and the key 4 turns off. Due to mutual induction, between sections 10-13 and 13-12 of inductive accumulator 2, the current is intercepted into section 10-13 and flows through circuit 9-3-10-13-6-8-7-7-14 again. Through the arc gap 8, a positive current pulse is again formed. The charge of the inductive accumulator 2 energy and the increase of the current in the arc circuit can occur both for several periods and for one half-period depending on the ratio of the pulse pulsing period and the value of the time constant of the inductive drive sections. In the steady state, the current value remains constant. The amplitudes of the forward and reverse polarity current pulses are determined by the magnitude of the stored energy in the inductive storage device and the ratio of the inductances of its sections. Duration

2

current pulses and their frequency are determined only by the moments of switching keys. By choosing different ratios of inductances of sections 10-13 and 13-12, for example, by changing the number of turns, the ratio of the amplitudes of the currents of the direct and reverse polarities can be adjusted. By changing the control unit 5 moments of switching keys 3 and 4, you can adjust the frequency and ratio of the durations of the pulses of currents of different polarities.

Adjusting the ratio of the amplitudes of currents of different polarities by changing the number of turns of the sections of the inductive storage device is performed discretely. To smoothly adjust this ratio, within discrete changes in the turns of mutually inductively connected sections, third 16 and fourth 17 control keys can be entered into the welding current pulse generator, which are connected in parallel with inductive drive 2 at points 10 and 12, and the junction of control keys 16 and 17 is connected to the second output terminal 7.

In this case, the control unit 5 is drying, and the antiphase operation of the keys 3 and 17, as well as 4 and 1b, with the pairs of keys 3 and 17, 4 and 16 working alternately. The duration of the on state of all keys, as well as the duration of operation of each of the above key pairs, are regulated.

The welding current pulse generator of FIG. 1 in this case works as follows. Consider his work in the steady state, when all the transition processes are over. At the initial moment of time t (Fig. 4), the arc is excited, block 5 turns on key 3, the other keys are turned off. A current of size I flows through section 10-13, the current flows along the circuit 9-3-10-13-6-8-7-14. At the same time, section 10-13 of inductive energy storage 2 energy through the switched on key 3 and arc gap 8 It is fed from the power source 1. The current through the arc gap increases. At the moment t it reaches the value 3; „. In this case, the control unit 5, the key 3 is locked, and the key 17 is turned on. The current closes on circuit 10-13 - 6-8-7-17. Power source 1 from

the welding circuit is turned off and the current through the arc is maintained by the energy stored in inductive storage 2. At this, the inductive storage is discharged and the current in the circuit decreases. At time t, when the current decreases to the value, control unit 5 turns on key 3 again, and key 17 is turned off. In this case, the charge of the inductive storage device 2 again occurs and the current in the arc circuit increases. Further, during the time of formation of a positive current pulse, the generator operates in a similar way. The magnitude of the current in the welding circuit is determined by the ratio of the time t - t, the charge of the inductive storage device 2 to

time t.

- t, its bit.

Than

the greater this ratio, the greater the average current of positive polarity. At time t, the current decreases to a value. Let's thicken, at this moment it is necessary to change the polarity of the current through the arc to the opposite. To do this, keys 3 and 17 are turned off, and the second pair of keys 4 and 16 begins to work. Suppose, at time t, key 4 is first turned on, while key 16 is locked. Due to the mutual induction between sections 10-13 and the current is intercepted in section 13-12 and flows through the circuit 13-12 - A - 11-14-7-8-6-13. During the time t, - t. section 13-12 inductive

1V, /

Accumulator 2 through the switched on key h and the arc gap 8 is charged from the power source 1. The current through the arc gap 8 abruptly changes its direction and increases in absolute value from the value at time t-j to the value at time t. At time t, key 4 is locked

with

control unit 5, and key 16 is turned on. The current is closed along circuit 13 - 12-16-7-8-6-13. The power source 1 is disconnected from the welding circuit, and the current through the arc is maintained by the energy stored in the inductive energy storage device 2. The inductive storage device 2 is then discharged and the current in the circuit decreases. At time t.

when the current decreases to

3, the control unit 5 turns on the key 4 again, and the key 16 turns off. In this case, the charge of the inductive storage device 2 again occurs and the current in the arc circuit increases. Next for Negative Formation.

ten

15

,

20

25

thirty

35

40

45

50

55

126

The current pulse current generator works in a similar way. The magnitude of the current in the welding circuit is determined by the ratio

time t - t „inductive charge

about drive 2 to time tg - tg it

bit The larger this ratio, the greater the average current of negative polarity flows through the arc. Thus, by changing the ratio of the charge time and the discharge time of the inductive storage device 2, using the control unit 5, the magnitude of the currents of different polarities can be independently and smoothly controlled. Changing the moments t and t, you can smoothly adjust the duration of the pulses of currents of different polarities.

In the manufacture of partitioned inductive drives, it is not possible to provide absolute magnetic coupling between the sections. Therefore, each section has a small inherent dissipation inductance. This leads to the fact that a change in the polarity of the arc current does not occur instantaneously, but within a certain time. In connection with this, the speed of the passage of current through zero decreases, which impairs the stability of the arc. The overvoltages on the controlled keys also increase, and to reduce them it is necessary to apply special measures that complicate the manufacture and commissioning of the generator.

To reduce the negative effect of these phenomena in the welding current pulse generator, an inductive filler can be applied, made in the form of two magnetically unrelated sections, and the fifth 18 and sixth 19 control keys are inserted, which are connected in series and connected in parallel with the inductive drive energy at points 10 and 12, with the connection point of the controlled keys connected to the first output terminal 6 (Fig. 5).

The control unit 5 in this case performs the antiphase operation of the keys 3, 19 and 4, 18 so that the state of the keys is

3 and 19 always corresponded to the off state of the keys 18 and 4, and the on state of the keys 1B and

4 - the off state of the keys 3 and 19. The duration and frequency of the on state of the keys are regulated.

 r

FIG. 6 curve 20 - current graph through section 10-13, curve 21 - current graph through section 13-12, curve 22 - current curve through an arc gap 8.

The welding current pulse generator of FIG. 5 works as follows.

At the time tp (Fig. 6), the arc gap 8 is brought to a conducting state. This can be done using, for example, an oscillator or by touching the electrode to the surface of the product. When a control signal is applied from block 5 to controllable keys 3 and 19, they are turned on. In this case, section 10-13 through the switched on key 3 and the arc gap 8 is charged from the power source 1. The current flows through circuit 9 - 3 - 10-13-.6-8-7- 14. This increases the current in both the circuit of section 10-13 and in the arc circuit. The current in section 13-12 is zero. At time t,

in block 5, controllable keys 3 and 19 are turned off, and keys 4 and 18 are turned on. The current in the circuit is abruptly reduced to zero. Section 13-12 through the switched on key 4 is connected to the power source 1 through the arc gap 8 and is charged. The current flows through the circuit 14-7-8-6-13-12-4-11-14. At the same time, the current in the arc circuit increases in the opposite direction along with the current of section 13-12, and the current in section 10-13 decreases the flow through chains 10-13-18 - 10, due to the dissipation of its energy on the internal resistance and the resistances of the key 18, connecting wires and contact connections. At time tj, the currents in both sections are non-zero, and with block 5, keys 3 and 19 are turned on again, and keys 4 and 18 are turned off. In this case, the arc current abruptly changes its direction and becomes equal to the current of section 10-13, which is charged again. The current increases in the arc circuit and section 10-13, the flow through circuit 9 is 3-10-13-6-8-7-14-9, and the current of section 13-12 decreases, the flow through circuit J3 is 12-16 19 , due to dissipation of its energy on the internal resistance and resistances of the key 19, connecting wires and contact connections. At time t. The currents in both sections are not zero, the control unit 5 turns on the keys -4 and 18 again, and the keys 3 and 19 are turned off.

In this case, the arc current abruptly changes its direction and becomes equal to the current of section 13-12, which is charged again. Further, the welding current pulse generator of FIG. 5 works in a similar way. By choosing different ratios of inductances of sections 10-13 and 13-12, due to, for example, changing the number of turns, the ratio of the amplitudes of the currents of the direct and reverse polarities can be adjusted. By changing the control unit 5 to the moments of switching the keys 3, 4, 18 and 19, it is possible to adjust the frequency and ratio of the durations of the pulses of currents of different polarities.

Controlled keys made on fully controllable semiconductor devices (transistors, optoelectronic devices, lockable trinistors) can at the present time ensure efficient switching of relatively small currents. At currents of hundreds of amps, it is more expedient to use incompletely controlled devices — thyristors, which are equipped with artificial switching nodes. In particular, at least one of the keys, for example, the key 3, to the welding current pulse generator, can be made in the form of a thyristor bridge switch (FIG. 7) on thyristors 23-26 with a capacitor 27 in the diagonal.

Depending on the thyristor control algorithm 23 - 26, the switch can operate in several modes.

In the first mode, the thyristors 23 and 24 are power, and the thyristors 25 and 26 are commutating. To turn on the switch, control signals are simultaneously applied to the thyristors 23 and 24, they turn on and the current flows through the switch. To turn off the switch, one of the thyristors 23 or

24 is locked. Locking is performed by applying a control signal to one of the switching thyristors.

25 or 26 depending on the polarity of the voltage of the precharged capacitor 27. If the polarity on it is as in FIG. 7 without brackets, the control signal is applied to the thyristor 25. In this case, the opposite voltage is applied to the thyristor 23 through the open thyristor 25 and it is locked. Current through switch

A3

As the recharge of the capacitor 27 decreases to zero. If the polarity of the voltage on the capacitor 27 is the same as that shown in parentheses, then the control signal is applied to the thyristor 26. This closes the power thyristor 24.

For the next switch on, the control signal is again applied to both thyristors 23 and 24.

In the second mode of operation, thyristor pairs 23, 26 and 24, 25 are alternately located at the opposite shoulders of the bridge.

When the thyristors 23 and 26 are turned on, the capacitor 27, having the voltage polarity shown in brackets, is recharged through the thyristors 23 and 26 and the external circuit. When it is recharged to the required voltage level in polarity without brackets, the thyristors 24 and 25 turn on. The thyristors 23 and

26 a reverse voltage is applied and they are locked. The capacitor 27 begins to recharge in reverse polarity through the thyristors 24 and 25 and the external circuit. Thus, due to the cyclic recharging of the capacitor

The switch 27 passes current as long as control signals are applied to the thyristors 23-26. In the case of control signals, the cyclic recharge of the capacitor is disrupted and the current through the switch ceases.

It is advisable to use the first mode of the switch operation with a relatively low frequency of the switch. In this case, the installed power of the thyristors is small. With an increase in the frequency of the pulses, the installed power of the thyristors increases At high frequencies (several kilohertz), it is advisable to use the second mode of operation, which allows one to obtain a higher limit switching frequency.

Compared with the known generator has the following advantages.

In order to compensate for disturbing effects on the arc and to stabilize its burning in the inductive accumulator of the prototype, a minimum energy supply A is necessary. In addition, an additional energy supply A, is necessary to conduct the current through the arc during one of the pulses. Thus, the maximum energy A, which must be made inductive on

five

five

0

five

21

five

2 o

KOPITOL1, prototype, LL + L. If energy and letters will be; less, then either the arcs will burn unstably, or the necessary duration will not be provided.P1, the continuity of the flow of current pulses, leading to the appearance of a current-free pause in the arc and the termination of the welding process.

In the proposed generator, the energy stored in an inductive storage device can be significantly lower than financed only by energy, which is necessary for stable arc burning. In this case, the maintenance of the necessary stability of the current pulse is carried out not at the expense of the energy stored in the inductive storage device, but at the expense of the energy consumed from the power source. This can reduce the inductance of the sections of the inductive storage device and, consequently, reduce the weight, size and consumption of active materials for its manufacture.

A smaller supply of energy in an inductive storage device allows the use of power sources with a lower no-load voltage, which also improves the weight and size characteristics of the generator.

The duration of current flow of any polarity in the proposed generator is much longer. Practically it can be any and the generator can even be used for direct current welding of any polarity, which greatly expands its functionality. A wide range of parameters for welding current pulses improves the quality of the weld due to the possibility of setting the optimal parameters of pulses in each individual case, as well as rationally distribute the energy between the welded product and the tungsten electrode, which increases its durability and reduces the consumption of tungsten.

0

0

five

Claims (4)

1. Welding current pulse generator containing a power source, two-section inductive energy storage, first and second output terminals, between which an arc gap is included, first and second controlled keys, a control unit, the first output of the power source 55   13 through the first controlled key is connected to the first output of the inductive energy storage device, the second output of the power source through the second controlled key is connected to the second output of the inductive storage device, the first output terminal is connected to the outlet from the junction of the inductive storage device, and In order to improve the quality of the welded joint, the power source is made with a terminal from the midpoint, which is connected to the second output terminal. 2. The generator according to claim I, characterized in that. The third and fourth controllable keys are connected to it, connected to the control unit in series and connected in parallel with the inductive energy storage, and the connection point of the controllable keys is connected to the second output terminal. 3. The generator according to claim 1, about tl and -. This is because the inductive energy storage device is implemented in the form of two magnetically unrelated sections and the fifth and sixth control keys are inserted into it, which are connected to the control unit sequentially. and connected in parallel to an inductive energy storage device, the connection point of the controlled keys connected to the first output terminal. 4. The generator according to claim 1, of which is at least one of the controlled keys made in the form of a thyristor bridge switch with a capacitor in the diagonal. Lo P u 5 Pw T / ...and to t2 H I one Vi one J / .. „.)  / / " I I Ll t, g t2 i  m Jl tf tj Fyg.5 R .7 Compiled by V. Pu-chinsky Editor E. Slngan Tehred M. Didyk Proofreader V. But ha A080 / 13 Circulation 974 Subscription VNIIPI USSR State Committee for inventions and discoveries 113035, Moscow, Z-ZZ, Raushsk nab., 4/5 Production and printing company, Uzhgorod, st. Project, 4